静水压力对岩石在等离子体冲击下压裂效果的影响
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摘要
为了了解与掌握深井下水中放电冲击波对岩石的破碎作用规律,建立了静水压力高达35 MPa的电脉冲压裂装置,可模拟深井近3 000 m下的围压,并进行了不同静水压下等离子体冲击压裂实验。电脉冲压裂装置最高工作电压20 k V,最大储能40 k J。在0~25 MPa的静水压力条件下,对6块砂岩岩样进行了冲击压裂实验。实验结果表明,随着静水压力的升高,相同放电条件下压裂产生的裂缝长度和宽度明显降低。所以静水压力的升高将使得岩样损伤范围减小,孔隙度以及渗透率提升幅度下降。静水压力对冲击压裂后裂缝的形成、分布、生长具有明显的影响。与常压下形成的裂缝相比,施加围压后裂缝多集中在电极处,数量多,但是长度较短,存在不同程度的弯曲,甚至局部区域出现了环形裂缝。
In order to understand the fracture law of rock by shock wave in deep water,an electric pulse fracturing device with hydrostatic pressure up to 35 MPa was established,which can simulate the confining pressure of 3 000 m underground. The experiments of plasma impact fracturing under different hydrostatic pressures were carried out. The maximum operating parameter of the fracturing device is 20 k V/40 k J. Six sandstones were fractured by electric pulse under the hydrostatic pressure which ranges from 0 to 25 MPa. The experimental results show that the length and width of fracture decrease significantly with the increase of hydrostatic pressure under the same energy. So the destroy range of shock wave decreases and the porosity and permeability decline with the increase of confining pressure. The hydrostatic pressure has obvious influence on the formation,distribution and growth of the crack after impact fracture. Compared with the cracks formed by atmospheric pressure,cracks are concentrated in the electrode. The number of cracks is more but the length is shorter and there are different degrees of bending,even annular cracks occur in the local area.
In order to understand the fracture law of rock by shock wave in deep water,an electric pulse fracturing device with hydrostatic pressure up to 35 MPa was established,which can simulate the confining pressure of 3 000 m underground. The experiments of plasma impact fracturing under different hydrostatic pressures were carried out. The maximum operating parameter of the fracturing device is 20 k V/40 k J. Six sandstones were fractured by electric pulse under the hydrostatic pressure which ranges from 0 to 25 MPa. The experimental results show that the length and width of fracture decrease significantly with the increase of hydrostatic pressure under the same energy. So the destroy range of shock wave decreases and the porosity and permeability decline with the increase of confining pressure. The hydrostatic pressure has obvious influence on the formation,distribution and growth of the crack after impact fracture. Compared with the cracks formed by atmospheric pressure,cracks are concentrated in the electrode. The number of cracks is more but the length is shorter and there are different degrees of bending,even annular cracks occur in the local area.
引文
[1]石崇兵,李传乐.高能气体压裂技术的发展趋势[J].西安石油学院学报,2000,15(5):17-21.SHI Chongbing,LI Chuanle.Development tendency of high energy gas fracturing technique[J].Journal of Xi’an Petroleum Institute,2000,15(5):17-21.
[2]张保平,方竞,田国荣,等.水力压裂中的近井筒效应[J].岩石力学与工程学报,2004,23(14):2476-2479.ZHANG Baoping,FANG Jing,TIAN Guorong,et al.Near wellbore effects in hydraulic fracturing[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(14):2476-2479.
[3]周健,陈勉,金衍,等.裂缝性储层水力裂缝扩展机理试验研究[J].石油学报,2007,28(5):109-113.ZHOU Jian,CHEN Mian,JIN Yan,et al.Experimental study on propagation mechanism of hydraulic fracture in naturally fractured reservoir[J].Acta Petrolei Sinica,2007,28(5):109-113.
[4]RUTGERS W R,JONG I D.Multi-tip sparker for the generation of acoustic pulses[J].Sensor Review,2003,23(1):55-59.
[5]SUN Y,FU R,FAN A,et al.Study of rock fracturing generated by pulsed discharging under confining pressure[C]∥2015 IEEE Pulsed Power Conference(PPC).Austin,TX,USA:IEEE,2015:1-4.DOI:10.1109/PPC.2015.7296927.
[6]BEES G L,TYDEMAN A.Capacitor charging power supply design for pulse to pulse repeatability applications[C]∥Digest of Technical Papers:12th IEEE International Pulsed Power Conference(Cat.No.99CH36358).Monterey,CA,USA:IEEE,1999,1:397-398.DOI:10.1109/PPC.1999.825494.
[7]BIEBACH J,EHRHART P,MULLER A,et al.Compact modular power supplies for superconduting inductive storage and for capacitor charging[J].IEEE Trans on Magnetics,2001,37(1):353-357.
[8]POLLARD B C,NELMS R M.Using the series parallel resonant converter in capacitor charging application[C]∥Proceedings of APEC’92 Seventh Annual Applied Power Electronics Conference and Exposition.MA,USA,USA:IEEE,1992:245-252.DOI:10.1109/APEC.1992.228405.
[9]杨小卫,严萍,孙鹞鸿,等.35k V/0.7A高压变频恒流充电电源[J].高电压技术,2006,32(5):54-56.YANG Xiaowei,YAN Ping,SUN Yaohong,et al.35k V/0.7A high voltage high frequency constant charging power supply[J].High Voltage Engineering,2006,32(5):54-56.
[10]FORSYTH A J,WARD G A,MOLLOV S V.Extended fundamental frequency analysis of the LCC resonant converter[J].IEEE Transactions on Power Electronics,2003,18(6):1286-1292.
[11]邵建设,严萍.高压电容器充电电源谐振变换器的定频控制[J].高电压技术,2006,32(11):107-110.SHAO Jianshe,YAN Ping.Constant switching frequency control of resonant converter of high voltage capacitor charging power supply[J].High Voltage Engineering,2006,32(11):107-110.
[12]苏建仓,王利民,丁永忠,等.串联谐振充电电源分析与设计[J].强激光与粒子束,2004,16(12):1611-1614.SU Jiancang,WANG Limin,DING Yongzhong,et al.Analysis and design of series resonant charging power supply[J].High Power Laser and Particle Beams,2004,16(12):1611-1614.
[13]NELMS R M,SCHATZ J E.A capacitor charging power supply utilizing a ward converter[J].IEEE Transactions on Industrial Electronics,1992,39(5):421-428.
[14]张东辉,严萍.高压电容器充电电源的研究[J].高电压技术,2008,34(7):1450-1455.ZHANG Donghui,YAN Ping.Development in high voltage capacitor charging power supply[J].High Voltage Engineering,2008,34(7):1450-1455.
[2]张保平,方竞,田国荣,等.水力压裂中的近井筒效应[J].岩石力学与工程学报,2004,23(14):2476-2479.ZHANG Baoping,FANG Jing,TIAN Guorong,et al.Near wellbore effects in hydraulic fracturing[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(14):2476-2479.
[3]周健,陈勉,金衍,等.裂缝性储层水力裂缝扩展机理试验研究[J].石油学报,2007,28(5):109-113.ZHOU Jian,CHEN Mian,JIN Yan,et al.Experimental study on propagation mechanism of hydraulic fracture in naturally fractured reservoir[J].Acta Petrolei Sinica,2007,28(5):109-113.
[4]RUTGERS W R,JONG I D.Multi-tip sparker for the generation of acoustic pulses[J].Sensor Review,2003,23(1):55-59.
[5]SUN Y,FU R,FAN A,et al.Study of rock fracturing generated by pulsed discharging under confining pressure[C]∥2015 IEEE Pulsed Power Conference(PPC).Austin,TX,USA:IEEE,2015:1-4.DOI:10.1109/PPC.2015.7296927.
[6]BEES G L,TYDEMAN A.Capacitor charging power supply design for pulse to pulse repeatability applications[C]∥Digest of Technical Papers:12th IEEE International Pulsed Power Conference(Cat.No.99CH36358).Monterey,CA,USA:IEEE,1999,1:397-398.DOI:10.1109/PPC.1999.825494.
[7]BIEBACH J,EHRHART P,MULLER A,et al.Compact modular power supplies for superconduting inductive storage and for capacitor charging[J].IEEE Trans on Magnetics,2001,37(1):353-357.
[8]POLLARD B C,NELMS R M.Using the series parallel resonant converter in capacitor charging application[C]∥Proceedings of APEC’92 Seventh Annual Applied Power Electronics Conference and Exposition.MA,USA,USA:IEEE,1992:245-252.DOI:10.1109/APEC.1992.228405.
[9]杨小卫,严萍,孙鹞鸿,等.35k V/0.7A高压变频恒流充电电源[J].高电压技术,2006,32(5):54-56.YANG Xiaowei,YAN Ping,SUN Yaohong,et al.35k V/0.7A high voltage high frequency constant charging power supply[J].High Voltage Engineering,2006,32(5):54-56.
[10]FORSYTH A J,WARD G A,MOLLOV S V.Extended fundamental frequency analysis of the LCC resonant converter[J].IEEE Transactions on Power Electronics,2003,18(6):1286-1292.
[11]邵建设,严萍.高压电容器充电电源谐振变换器的定频控制[J].高电压技术,2006,32(11):107-110.SHAO Jianshe,YAN Ping.Constant switching frequency control of resonant converter of high voltage capacitor charging power supply[J].High Voltage Engineering,2006,32(11):107-110.
[12]苏建仓,王利民,丁永忠,等.串联谐振充电电源分析与设计[J].强激光与粒子束,2004,16(12):1611-1614.SU Jiancang,WANG Limin,DING Yongzhong,et al.Analysis and design of series resonant charging power supply[J].High Power Laser and Particle Beams,2004,16(12):1611-1614.
[13]NELMS R M,SCHATZ J E.A capacitor charging power supply utilizing a ward converter[J].IEEE Transactions on Industrial Electronics,1992,39(5):421-428.
[14]张东辉,严萍.高压电容器充电电源的研究[J].高电压技术,2008,34(7):1450-1455.ZHANG Donghui,YAN Ping.Development in high voltage capacitor charging power supply[J].High Voltage Engineering,2008,34(7):1450-1455.